1. Field of the Invention
The present invention relates to a light-blocking shutter in fiber optic connector or adapter that prevents emission of laser light when the connector is open (i.e., when no mating connector is inserted). This prevents eye damage if a person should look into the open end of the connector that is carrying an optical signal. More specifically, the invention relates to light-blocking shutters that automatically block the opening through which the light signal is transmitted when a mating connector is removed and automatically open when the mating connector is inserted.
2. Description of the Prior Art
FIG. 3, labeled xe2x80x9cPrior Art,xe2x80x9d shows a typical connector tip with a ferrule F, having centrally-located optical fiber (or fibers) 0 terminating at its surface, extending from the end of a connector body B1. (B2 is an outer body that slides on B1.) Of course, damage to the end of the fiber itself(dirt or scratches) can also cause severe scattering of the light beam and insertion loss.
A number of patents disclose fiber-optic connectors with spring-loaded shutters that are pushed inward by the insertion of a male connector.
Abendschein et al 6,004, 043 discloses a spring-loaded shutter door that is disposed at an angle 0 inwardly into the receptacle and is pushed out of the way by the inserted male connector (column 3, lines 50-54). The inserted male connector contacts the shutter near the spring-loaded hinge, which requires a greater force than if the connector contacted the shutter at a distance from the spring-loaded hinge.
U.S. Pat. No. 6,142,676 to Lu shows an internal beam stop, door 38. Door 38 is biased by a spring 39 and limited by stop posts 40 (col. 4, lines 6-21). The door is angled at about 20xc2x0 off the transverse. As seen in FIGS. 23-27, the door 38 is first pushed inward by the cover 66 and then by a prong 76 (FIG. 24). Once the door 38 is held up out of the way, continued insertion operates a cam mechanism that raises a cover 66 (FIG. 26) so that it comes to rest against the raised door 38 (FIG. 27).
It is noted that slanting the shutter does not actually increase the leverage and does nothing to solve the leverage problem discussed above, as long as the engagement is laterally near to the hinge. This is because the torque required to open the shutter is the product of the force and the distance from the line of the force to the hinge. The line of force extends parallel to the motion of the male connector.
Roth, U.S. Pat. No. 6,108,482, states its object as preventing damage to the tip of a male optical-fiber connector (column 1, line 61 to column 2, line 6). Roth ""482 shows a spring-loaded shutter 28 in which the shutter surface 42 is divided into a recessed area 44 and a surrounding ledge 46 having a raised surface 42 (column 3, lines 47-49 and 59-61). The male connector that pushes open the shutter has a projecting optic fiber ferrule 54 with a xe2x80x9cfront mating facexe2x80x9d 54a that xe2x80x9cengages outer surface 42 of shutter 28 and automatically opens the shutterxe2x80x9d (column 4, lines 11-14). The shutter""s recess 44 is intended to protect the central area of the mating face 54, where the fiber termination is located: xe2x80x9cRecessed area 44 has a depth such that the polished ends of the optical fibers are protectedxe2x80x9d (column 4, line 17). The fiber termination, but not the ferrule itself, is protected.
Roth""s structure has several disadvantages. When the ferrule hits the shutter it is subjected to forces that would better be taken by the shoulder 56 of the connector body surrounding it. Roth actually teaches against opening the shutter by pushing it with anything except for the ferrule, stating that the recess xe2x80x9cshould be designed with a depth slightly less than the distance the ferrule projects from the fiber optic connectorxe2x80x9d (column 3, lines 53-55; see also column 2, lines 32-34).
In summary, the prior art does not disclose any fiber-optic light beam shutter that is swung open by a force exerted far from the hinge line, so as to prevent high loading and eventual damage to the hinge. Neither does it disclose a shutter that uses a simple, inexpensive, and foolproof structure to insure that the delicate tip of the inserted connector does not bang against the shutter, risking damage.
The present invention relates to a female or receptacle connector or adapter with a passage into which is inserted a mating male connector or plug, such as for example the SC connector shown in FIG. 3, in such a way that the fiber optic end O is aligned with and juxtaposed to another fiber end very precisely, so that light is transferred into (or from) the fiber end O. The adapter holds the other fiber. When that other fiber is active, light is emitted from its terminus and will shine out of the passage when the male connector is not inserted in the adapter passage. Since the light used in fiber optic communications is generated by lasers, people should not be exposed to the light. The recent trend toward more powerful signal lasers has made fiber optics more dangerous than they were previously.
The invention provides a shutter that is hinged on one side of the adapter passage. It is pushed out of the way by the male connector (e.g., that of FIG. 3) when the male connector is inserted. The shutter is spring-loaded so as to remain in a closed position until pushed open, and to spring back when the male connector is withdrawn.
Preferably, the shutter is made by chemical etching followed by forming. It may also be made by stamping. A preferred material is stainless steel, but plastic with 0% light transmission, or with a metallic coating, is also suitable. Any suitable materials and manufactures are within the scope of the invention.
The shutter includes a light-blocking panel portion and a shoulder portion. The shoulder portion is the first part to contact the male connector, and is placed so that only the shoulder of the body of the SC male connector, and not the ferrule, touches it. By taking all of the insertion force, the shoulder protects the delicate extending tip of the male connector (e.g., the ferrule F of FIG. 3).
The shoulder height in the longitudinal direction (the direction that is parallel to the run of the optical fiber) is shown as D in FIG. 6. This height or distance D should be greater than the distance the ferrule projects from the shoulder of the connector in the same longitudinal direction; that distance is shown as d in FIGS. 3 and 6. D being greater than d insures that the ferrule tip never touches the more interior parts of the shutter when the shutter shoulder is against the connector body.
To further protect the ferrule, the leading edge of the shoulder (the edge foremost in the longitudinal direction, that first contacts the inserted connector body) is preferably set back from the front surface of the adapter body by a longitudinal-depth distance greater than the shoulder height D (and therefore also greater than the longitudinal ferrule extension d). When this set-back is greater than d, the tip of the ferrule F will not touch the leading edge of the shoulder if the connector is inserted off-center.
The setback or longitudinal-depth distance not only helps to prevent ferrule contact, it also makes it more difficult to open the shutter with a finger, pencil, or the like because the shoulder is recessed into the adapter body.
It is also preferred that in the transverse direction (the direction perpendicular to the longitudinal direction), the separation between the side of the ferrule and the adjacent outside of the connector body exceeds the transverse distance from the side of the adapter body aperture to the top of the shoulder; that is, the ferrule is xe2x80x9cabovexe2x80x9d the shoulder. Such a relationship insures that when the outside of the male connector body is against the inside of the passage aperture, the ferrule does not touch the shoulder.
The connector housing includes a space into which the shutter is entirely recessed when the male connector is fully inserted.
Preferably there are two shoulders, one on either side of a central space, so that the shutter is generally C-shaped in cross section; the extending tip of male connector moves into the central space during insertion, while the ferrule-holder shoulder on either side pushes the respective shoulder. The two shoulders balance the force and eliminate a torque on the hinge that is perpendicular to the axis of the hinge.
The shoulders increase the mechanical advantage of the male connector in swinging the shutter out of the way. Besides extending along the insertion axis to protect the connector tip, the shoulders also extend away from the hinge line in a direction that is transverse to the insertion direction, i.e., toward the middle of the insertion passage. This increases the torque acting on the shutter relative to the hinge line, and makes for faster and easier shutter opening and decreased force on the shutter hinges.